Revealing the Role of Coal Gangue-Biochar Composite for Removing SO42− from Water: Adsorption Mechanisms and Application Effects

Sulfate ions are commonly found in water, but excessive concentrations of these ions can have detrimental effects on the aquatic environment. In this study, reed straw was chosen as the raw material for producing biochar, which was then pyrolyzed with coal gangue to create environmentally friendly adsorption materials. This innovative approach aims to combat the issue of elevated SO42− concentrations in water while efficiently utilizing solid waste. The results showed that the adsorption process best fit the when the was pH 2 and the dosage was 8 g·L−1, and the adsorption capacity reached the maximum of 49.56 mg·g−1. Via extensive characterization, kinetic studies, and isotherm experiments on the modified biochar, we determined that the mechanism of SO42− adsorption primarily involves electrostatic adsorption, physical adsorption, and chemical adsorption. The toxicology experiments showed that the activity of antioxidant enzymes and the amount of malondialdehyde decreased, and the content of chlorophyll and soluble protein increased. These findings suggest that modified biochar can mitigate the harmful effects of SO42− on reeds to a certain extent, ultimately promoting the growth of these plants.